Tempering cellulose acetate plastics



patented Nov. 6 1934 PATENT QFFECE TEMPERING CELLULOSE ACETATE PLASTICS Amerigo F. Caprio, Newark, N. 3., assignor to Celluloid Corporation, a corporation of New Jersey No Drawing. Application April 12, 1929, Serial No. 354,705

2 Claims.

The tendency of cellulose acetate compositions is to exhibit either excessive softness or undue hardness. Between these two extremes is the middle ground or conditional balance of good strength and a hardness compatible with fabrication requirements. To attain such balance of quality it is customary to make delicate adjustments of plasticizers, solvents, character of base and proportions. But in spite of these precau- .Ztions the cellulose acetate plastics are occasionally more or less obj ectionally hard or even brittle, especially in cold weather. Many attempts have been made to produce and particularly to restore this condition of balanced quality in cellulose acetate compositions but with indifferent success.

An object of this invention, therefore, is to provide a process for tempering cellulosic plastics.

A further object of this invention is to provide a process for restoring to pliability, and strength, brittle cellulose acetate plastic material.

A further object of this invention is to provide strong cellulose acetate materials and a process for making same.

Many other objects and advantages will appear to persons skilled in the art, as the specification proceeds.

After considerable experimentation, I have invented the process whereby a certain degree of water penetration is availed of to produce or regenerate a strong pliable cellulose acetate composition, otherwise stubborn hard and brittle.

The process comprises soaking the material or blanks for a certain length of time, depending more or less upon the thickness of the stock, in substantially plain water, preferably at room temperature. By room temperature, is meant any of the varying temperatures of work rooms. While I prefer room temperatures, it is obvious that temperatures above and below may be used, without 4, ;departing from the spirit of the invention. However, I do not depend on different temperatures for a softening or any other effect.

There probably is not a complete penetration of moisture throughout the mass, in fact there is apparently only a partial impregnation. The process is particularly valuable in the art inasmuch as any evaporation of water on exposure, takes place Without a warping efiect on the shapes or articles made from the water-tempered material. A treatment covering a period of one half hour or more, is recommended for material of an average thickness or volume of plastic substance, such as blanks for brush and mirror backs, combs, handles, etc. A desirable tempering of moderately thin sheets or pieces can be accomplished in much less time, often in ten minutes. The operator must use his judgment, and be guided by the particular results desired, as is done on other fine operations of fabrication or shaping. He will appreciate the simplicity of the new method and its great value in bringing the material to the right condition.

Compounds made with a plasticizer soluble or partly soluble in Water such as methyl acetanilid, dibutyl tartrate, triacetin, toluene sulphamid etc. 5 seem to demand a shorter soaking time than compounds containing plasticizers which are water resistant, for instance, triphenyl phosphate, tricresyl phosphate, paraethyltoluolsulphonamid, etc.

I am aware that nitrocellulose compositions, which are of course, of inorganic character and quite distinct in that respect, may be toughened slightly by treatment with water, but this did not lead to the development and invention of this novel process for the tempering of cellulose acetate plastics, for I was compelled to make experiments and trials with the attainment of tempering efiects quite distinct from the stubborn action of water soaked pyroxylin plastics. The tempered result of my process is hard and substantially nonshrinkable and apparently represents a slight but necessary change in the cellulose acetate base. The process corrects hurtful conditions and increases output through stoppage of waste.

It is of course understood that the cellulose acetate composition may contain pigments, dyes, fillers, eiiect materials, etc.

In treating pyroxylin plastics it has long been customary and apparently necessary to add alcohol or other liquid solvent to the water in order to get penetration and toughness. The addition of other substances is unnecessary in my process. I do not depend upon a solvent attack of tempering liquid on the material, such as is common in the case of nitrocellulose, for, among other things, such solvent attack has a warping erlect on the material. It is to be noted that my tempering agent, will temper a cellulose acetate composition which contains plasticizers insoluble in water or actually water repellent, such, for example, as the organic phosphates. It is, of course, understood that the tempering fluid need not be absolutely pure water. Small amounts of dissolved or suspended matter may be present, without departing from the spirit of the invention. This includes any of the solvents for cellulose acetate, providing such solvents are not pres- 110 with solvents, then drying out the volatile elements until hardness or brittleness ensues, and finally converting the composition into a strong tempered mass by soaking in water substantially free from solvent.

2. Cellulose acetate plastic material comprising cellulose acetate and a plasticizer tempered by soaking in water substantially free from solvent.

AMERIGO F. CAPRIO. 

